There have been quite a few posts about this on this forum and a lot of others. I'm going to use
Lizard Skin on mine. It's a spray application type. It's gotten good feed back from those that have tried it. Plus it has thermal properties that the Dynamat does not have unless you by the liner that goes on top of that. (That is the Dynamat Xtreme.) Another bad point besides the cost is the weight. I'm trying to keep my truck on a diet and don't want to add all that weight. Don't get me wrong, Dynamat is the best stuff out there IMO.
Fatmat calls itself the Dynamat Xtreme alternative so you might want to try them out. Mr Gasket has recently came out with this
stuff. Don't know of anybody who's tried it. Here's some stuff sold by
Route 66. There is also Brown Bread from
B-Quiet. It also compares itself to Dynamat. Actually, Brown Bread has been replaced by what they now call Ultimate.
Basically, I've done a lot of research. What your after is the NVH values of the products. Make sure you read the fine print as some of the liners require a second material OVER them to control heat. If that's not a issue then no problem. Most of the paintable types do not have any thermal protection. A lot of the products have changed since they first hit the market. Dynamat being one of them (due to odor). I think the Fatmat or B-Quiet products will give you good performance for the money. There has been some issues with installing the cheaper stuff to roofs and it not staying after the sun had been beating on it but we are dealing with trucks so that will not be a issue. Also most of these products don't cut down noise a whole lot. If decreasing noise is your goal, get some Fatmat or B-Quiet and put in the doors and maybe firewall and get the good 1" jute padding under the carpet. Make sure all holes are sealed in the firewall and floor.